In the past many devices have been used within hopper type containers to maintain a continuous flow of particulates through the container. Such devices are often needed when materials such as coal, ore, sand and other particulate materials tend to rathole or become impacted within the container particularly when they are of certain external shapes or surfaces or are mixed with water or a bonding agent or exposed to freezing temperatures.
Some of the hoppers have been equipped with vibrators for shaking the container or its walls to dislodge the particulate matter and induce a flow through the container. In some instances jets of high pressure air have been introduced into the material to start and maintain its continuous flow through the receptacle.
In addition to these techniques various types of inflatable bags have been placed on the inner walls of the containers and alternately inflated and deflated to create a varying pressure against the particulate matter and break such jams or icing of the material. A typical example of such device is shown in U.S. Pat. No. 2,646,905 issued to W. R. Vincent. Such device operates somewhat on the principle of the inflatable deicers used on aircraft wings, such as that on U.S. Pat. No. 2,536,739 issued to H. E. Greene. The above mentioned Vincent patent appears to be one of the closest prior art patents known to the inventor of the invention described in this specification.